The thesis entitle a comparative study of the concept of selflessness in Theravada Buddhist philosophy and Jean Paul Sartre is aim at a study of the concept of Anattã in Theravada Buddhist philosophy and Sartre’s philosophy and to compare the similarity and contradiction of the both philosophic thought. This thesis was conducted by the documentary research, all the primary and secondary documents both English and Thai on the Selflessness of Theravada Buddhist philosophy and Sartre were used in this thesis.

              The study found that the concept of Selflessness in Theravada Buddhist Philosophy and Jean-Paul Sartre are likely the same. All compounded things in the world matter and mind is the state of Selflessness. It is said that the Selflessness is the most important factor of everything. Since the mind forming everything make us not see the state of Selflessness. This leads us to misunderstand that there is no Anatta. Anatta is just the concept of thinking created by human beings. Absolutely, there is nothing.  Everything in Buddhist Philosophy, being and non-being, is the state of emptiness. Human beings were by covered ignorance (avijja) then they cannot realize the law of the Three Characteristics and these made man clings to everything as their Atta (Self) and can be possessed.

              The difference points of non-self between Sartre and Theravada Buddhist philosophy seem to be very similar but if it is realized in deep it can be found that Jean-Paul Sartre’s Selflessness supports the concept of freedom which comes out of interference, force and power. The process of choosing to do or not to do by one’s self is also included here. In the other hands, the theory of selflessness was used by Sartre to refuse other school of philosophy that holds self as its center.

              In this point Sartre urged man to seek out themselves in order to fulfill something and made man valuable. The result of these made man suffer that arisen from the alienation and delusion. To seek out something outside is not the absolute happiness of man. Sartre did not mention the way to get rid of self or Atta or stop to search the external things and turn to seek out the happiness in one’s mind.

However the Theravada Buddhist philosophy aims at the seeking of the internal happiness or the freedom of mind more than the external happiness or the outside freedom. That is to say, happiness that arises from the material thing is not the absolute happiness. The absolute happiness creates from the external and internal freedom of man mind and never falls into ignorance, desire and delusion.